Conventional formwork structure is well known in the art of casting concrete and in general such formwork is composed of shutters made of wood or plastic which are assembled in various ways to constitute the desired form. After the concrete has been cast the form is disassembled for subsequent use.
Conventionally, various types of fasteners are employed to secure the shutters to one another and in the disassembly it is necessary to remove the fasteners. This involves considerable time and effort and frequently the forms become broken as a result of the removal of the fasteners.
An object of the invention is to provide a formwork which is readily disassemblable and which does not rely upon the use of fasteners to assemble juxtaposed elements of the form.
It is a further object of the invention to provide formwork of the above type in which assembly between juxtaposed elements is simply made through the provision of a slidable locking engagement therewith.
In accordance with the invention, there is provided formwork for casting concrete comprising a plurality of flattened tubular elongated elements each having one wall with an outer surface for contacting cast concrete and an opposite wall with aperture means thereon, and retainer means disengagably interfittable with at least two of said elongated elements to hold the same in assembled juxtaposed relation, said retainer means including projection means for penetrating into the interior of each elongated element through the aperture means thereof while engaging that wall of such elongated element which is provided with the aperture means.
In further accordance with the invention the aperture means in each said tubular elongated element is constituted by a series of longitudinal aligned apertures of trapezoidal shape.
The invention further contemplates that said retainer means includes two flanges with notches therein, said flanges being engageable in said apertures of the elongated elements with said notches receiving the walls bounding the apertures.
In order to connect two elongated elements which are at right angles to one another, the flanges extend at right angles on the retainer means. When two elongated elements are to be connected which extend parallel to one another a retainer means is employed in which the flanges extend parallel to one another.
The invention further contemplates the use of a manually engageable extension arm on the retainer and a stirrup in the form of an angle member can be secured to the extension arm for supporting and positioning planking on said arm.
According to a feature of the invention the retainer can be provided with pins for receiving tie down means which holds the formwork assembly in place and resists the bouyancy effect of the cast concrete.
According to a further feature of the invention, the apertures in the tubular elements are of trapezoidal shape and the flanges are dimensioned relative to the trapezoidal apertures to be insertable thereinto and moveable downwardly so that the notches in the flanges receive the walls of the elements at the lower ends of the apertures producing a force on the elements urging them against one another in a secured juxtaposed relation.